Hertzian elasticity and triggered swelling kinetics of poly(amino ester)-based gel beads with controlled hydrophilicity and functionality: A mild and convenient synthesis via dropwise freezing into cryogenic liquid

Ökten, Nur Sena
Çanakçı, Cahit Can
Orakdoğen, Narin
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Poly(amino ester)-based homo- and co-polymeric gel beads were prepared via "dropwise freezing into cryogenic liquid" method and multi-responsive properties of the prepared spherical beads were confirmed by the pulsatile swelling kinetics and the stress-strain relationships based on Hertzian elasticity. Dual pH- and ionic strength-responsive homopolymeric PDMAEMA as well as copolymeric poly(hydroxyethyl methacrylate-co-dimethylaminoethyl methacrylate) P(HEMA-co-DMAEMA) gel beads crosslinked with diethyleneglycol dimethacrylate (DEGDMA) were prepared by aqueous phase crosslinking copolymerization at subzero temperature within the millimeter-sized frozen droplets in the paraffin oil as continuous phase. With this method, spherical ionic gel beads of sizes 2-5 mm could be synthesized without using a stabilizer. The successful synthesis of PDMAEMA and P(HEMA-co-DMAEMA) gel beads was confirmed by ATR-FTIR and SEM. Modulus of elasticity of cross-linked poly(amino ester)-based gel beads in swollen state was measured as a function of the bead diameter. The relationship between the compressive elastic force and corresponding deformation was obtained to compare the experimental results with theoretical-analytical formulations using the constitutive relations from Hertzian elasticity. The effective crosslink density of gel beads produced in the same synthesis batch increased as a function of increasing bead diameter, which was attributed to the formation conditions of the beads via frozen droplets of the pre-gel solution. The synthesis pathway used for the production of gel beads from methacrylate-based monomer with a polar tertiary amino group offered one-way control over material geometry to design soft and smart materials with controlled size and porosity.
Hertzian Elasticity, Gel Beads, Hydroxyethyl Methacrylate, Dimethylaminoethyl Methacrylate, Swelling, Diffusion, Hertz Esnekliği, Jel Boncuklar, Hidroksietil Metakrilat, Dimetilaminoetil Metakrilat, Şişme, Yayılma